This invention relates to automotive passenger restraint systems, and more particularly to a control method that differentiates deployment events from non-deployment events.
In general, automotive passenger restraint systems perform a number of functions including acceleration sensing, signal processing and analysis, and deployment of one or more restraint devices such as frontal or side air bags and seat belt pretensioners in response to a sensed crash event. Typically, the acceleration signal is monitored to detect a potential crash event, and then filtered or integrated over the course of the crash event to produce a velocity change or xcex94V signal. If the xcex94V signal exceeds a threshold, the crash event is determined to be sufficiently severe to warrant deployment of restraints. The threshold is typically time-dependent, and is calibrated based on data logged for different types of crash events, as well as data logged during rough road driving.
A problem with the above-described approach is that it is often difficult to synchronize the time progression of the crash (that is, the event clock or timer) with the actual crash event. As a result, it can be difficult to distinguish between deployment events and non-deployment events, particularly in the first portion of the sensed event.
The present invention is directed to an improved deployment control method for a vehicular supplemental restraint system having an acceleration sensor and a restraint device to be deployed for occupant protection in a crash event, where the deployment threshold is adaptively adjusted based on the magnitude and rate of change of the xcex94V signal and the progression level of the sensed event. Since the deployment threshold is adjusted as a function of the input (xcex94V) signal, the control is characterized herein as a feed-forward control.
According to the invention, the acceleration signal is filtered (integrated) to form the xcex94V signal, and the deployment threshold is periodically adjusted based on the rate of change (slope) of the xcex94V signal, if the magnitude of the xcex94V signal is within a xcex94V range specified for the progression level of the sensed event. Preferably, the maximum amount of adjustment is also specified based on the progression level of the event. As a result, the deployment threshold tends to follow or track the xcex94V signal, particularly for non-deployment events where the magnitude of the xcex94V signal is within the specified xcex94V range, thereby preventing deployment of the restraints. In deployment events, the magnitude of the xcex94V signal is more likely to fall outside the specified xcex94V range, which minimizes feed-forward adjustment of the deployment threshold, thereby minimizing any delay in deployment of the restraints.